Method and apparatus for access selection in a multiaccess communications system

ABSTRACT

The present invention relates to communications systems comprising multiple access technologies, and more especially it relates to access technology allocation of communications in such communications systems. Particularly, it relates to allocation of a plurality of communication flows to one or more of a plurality of access technologies avail able in the communications system. Access selection based upon stored one or more preference values is disclosed.

TECHNICAL FIELD

The present invention relates to communications systems comprisingmultiple access technologies, and more especially it relates to accesstechnology allocation of communications in such communications systems.Particularly, it relates to allocation of a plurality of communicationflows to one or more of a plurality of access technologies available inthe communications system. Such technologies include, e.g., wirelessaccess technologies such as radio access technologies and optical accesstechnologies.

BACKGROUND

Communications comprising a plurality of access technologies havereceived great interest. Well known examples are dual mode telephonessuch as DECT/GSM phones and GSM/WCDMA phones. DECT (Digital EnhancedCordless Telephone) is a radio access technology, RAT, applying GaussianMinimum Shift Keying, GMSK, combining 10 carriers of frequency divisionmultiplex, FDM, and 12 slots of time division multiplex, TDM, for eachof uplink and downlink directions applying time division duplex, TDD,sending uplink and downlink communications separated in time. GSM(Global System for Mobile Communications) also applies GMSK, FDM and TDMbut, in contrast to DECT, applies frequency division duplex, FDD,sending communications in uplink and downlink directions on differentfrequencies. WCDMA (Wideband Code Division Multiple Access) alsoseparates uplink and downlink directions in frequency in FDD-mode ofUMTS, applying code division multiple access for multi-user access.

Ouyang Congxing, Wang Bin, Wang Xiaoqi, Wei Bing and Huang Yuhong, ‘Ananalysis of radio handover success ratio,’ Huawei Technologies, November2005, Issue 19, analyzes factors that may affect handover success ratiowith inter-RAT handover. The inter-RAT handover includes the steps of

-   -   1. Measurement;    -   2. Judgement; and    -   3. Implementation.

The Measurement step teaches about signal level, signal quality andsynchronization information of target RAT. In the Judgement step, theMeasurement results are reported to the source side, or source RAT. Thesource side or the terminal may determine on whether or not to actuallyhandover to the target RAT. In the latter case, the terminal willdirectly establish the connection with the target side wireless systemcell. In the former case, the source side notifies the target side toprepare the corresponding channel resource and then the source sidesystem issues the handover command to notify the terminal to transfer tothe target side wireless system. The authors conclude that networkplanning will be crucial, including settings of proper handover judgmentthresholds and handover delay time. A fast fading signal at the targetside is a primary reason for inter-RAT handover failure.

Eva Gustafsson, Annika Jonsson, ‘Always Best Connected,’ IEEE WirelessCommunications, February 2003, describes the concept of Always BestConnected, ABC. The paper discusses user experience and businessrelationships to broaden third generation cellular systems, 3G, such asUniversal Mobile Telecommunications System (UMTS) or CDMA2000. Thefundamentals of the ABC concept are that a user shall always beconnected through the best available device and access technology at alltimes. The definition of best, the B in ABC, depends on a number ofdifferent aspects such as personal preferences, size and capabilities ofthe device, application requirements, security, operator or corporatepolicies, available network resources and network coverage. Depending onthe applications and user preferences, a user can be connected over oneaccess at a time or over multiple accesses in parallel. The ABC conceptholds for virtually all types of access technologies including thosethat are yet to come. In its simplest form, an ABC service provides theuser with capabilities to access services of different types of networktechnologies, without mobility support. Gustafsson and Jonsson describeexample scenarios of a user named Hubert. In one scenario Hubert has aPDA (Personal Digital Assistant) and a laptop, both of which havebuilt-in 3G capabilities. In another scenario the laptop and the PDA arepart of Hubert's personal area network, PAN, communicating overshort-range radio technology, e.g. Bluetooth. In the example, the PANalso includes Hubert's 3G mobile phone. An ABC terminal may be inclusiveor exclusive of access devices. In the former case, the terminalperforms access discovery periodically and at startup to find out thebest available access technology. In the latter case, the accessdiscovery is an internal functionality of the device as long as there isonly one device. When there is a plurality of devices including accessdevices connected in a PAN, the ABC terminal needs to find out whichaccess devices are available in the PAN. Key issues for providing ABCaccess discovery for a PAN are:

-   -   Defining a generic set of parameters describing access networks        and devices. Examples of such parameters are type of access        network technology, access network operator, QoS (Quality of        Service), current cost for a particular user to connect over a        particular network, type of access device, and type of        connectivity the access device can offer;    -   Investigating how the statistics of the access networks should        be collected, e.g. in terms of measurements, information from        operators and so on;    -   In a PAN, handling the dynamics of the PAN in terms of access        devices becoming available or unavailable as the PAN        configuration changes.

Access selection refers to the process of deciding over which accessnetwork to connect at any point in time. Gustafsson and Jonsson identifythree parts of such a process:

-   -   1. Terminal-based selection;    -   2. Network-based selection; and    -   3. User intervention.

When selecting access network, a number of different aspects areconsidered, such as ABC user preferences, service provider preferences,available bandwidth, cost and operator, device capabilities andapplication requirements. An ABC terminal needs a stored profile orpriority list, or default setting for choosing access network at startupor reconnection. Otherwise, it cannot benefit from any network-basedfunctionality. A benefit of network-based support for access selection,or network-based access selection is that an ABC service provider couldtransfer network-specific information to the terminal. Network-basedaccess selection allows for load balancing, and may reduce signalingover the radio interface if the selection process requires repeatedinquiries to databases in the network. Network-based support for accessselection makes it possible to perform radio-resource-efficientselection in order to maximize total system throughput.

Gustafsson and Jonsson describe different approaches for contentadaptation.

-   -   1. One approach is for an application to detect changes in        network characteristics and/or device capabilities and request        the application server to adapt the contents accordingly.    -   2. A second approach is for the terminal to provide information        about the access network and device to either of the        application, the application server, or databases and servers in        the ABC service provider network.    -   3. A third approach is to let the access network provide        information to the application server and/or the device        regarding network characteristics (e.g., notification of QoS        changes).

Bo Xing and Nalini Venkatasubramanian, ‘Multi-Constraint Dynamic AccessSelection in Always Best Connected Networks,’ Proc. of The Second AnnualInt. Conf. on Mobile and Ubiquitous Systems: Networking and Services,Volume 00, 2005, Jul. 17-21, 2005, pp. 56-64, addresses the problem ofdynamic access selection, the concept of ABC enabling a new paradigm infourth generation mobile communication, 4G, systems. The authors modelthe problem of multi-constraint dynamic access selection, MCDAS, as avariant of bin packing problem. A series of approximation algorithmsderived from the First Fit Decreasing, FFD, algorithm are proposed forfinding near-optimal solutions in access selection comprising variousaccess technologies, such as Wi-Fi, Bluetooth, GPRS and UMTS,simultaneously available to mobile devices.

The optimizations incorporate the ability to adapt to varying loadconditions as well as dynamic network parameter changes caused by devicemobility. The proposed algorithms are compared to a quasi-optimaloff-line solution, obtained assuming full knowledge of all traffic flowsfor a set of inputs.

Access preference of a flow describes which access network is preferredby a traffic flow and to which extent. A power consumption cost modelcalculates the power consumption of a particular flow, f_(i), using aparticular access network, A_(j). A dissatisfaction value of eachtraffic flow assignment describes the degree to which the assignmentdoes not match the flow's access preference.

A bin packing problem, packing items into smallest number of bins ofgiven maximum size, is called on-line if every item is packed withoutinformation on subsequent items, while an off-line problem allowsdecisions to be made with full knowledge of all items.

FFD is a well-known algorithm for off-line packing items in bins, ofgiven maximum size packing the largest item into the first bin which hasenough remaining room, when the bins are ordered in sequence ofdecreasing fill-level (increasing remaining room).

G. P. Koudouridis, P. Karlsson, J. Lundsjö, A. Bria, M. Berg, L.Jorguseski, M. Meago, R. Agüero, J. Sachs., R. Karimi, ‘Multi-RadioAccess in Ambient Networks,’ IST EVEREST Workshop, Barcelona, Spain,November 2005, illustrates multi-radio access, MRA, for addressing thedynamics of ambient networks, ANs. Accessing any network, public orprivate, possibly without subscription, through instant establishment ofinter-network agreements is one of the strategic objectives of TheAmbient Networks project, an integrated project within The EU 1^(st)6^(th) Framework Program. Koudouridis et al. provide an overview ofevaluation studies for multi-radio access selection, MRAS, in terms ofefficient radio resource utilization.

For radio access selection, Koudouridis et al. propose a hierarchicaldistribution of functionality between multi-radio resource management,MRRM, and generic link layer, GLL, where the GLL dynamically handlesmapping of data flows to radio accesses, RAs, selected by MRRM. Thecriteria used for selection of access include: radio linkcharacteristics, cell load and capacity, RAT preferences, terminalcapabilities, terminal velocity, service type and required QoS.Multi-radio transmission diversity, MRTD, essentially refers to systemcapability of selecting on a relatively fine time-scale among pluralradio accesses for transmission of user data. Ultimately, MRTD selectsradio access on a per packet basis.

None of the cited documents above discloses a method and system ofaccess selection with flow bundling constraints, the access selectiondetermining and including one or more metrics in an access preferencelist of a Communications Flow Correlation Module.

SUMMARY

A communication flow is a stream of communicated information. When thereis a plurality of concurrent such streams they are generally referred toas flows or communication flows. Prior-art solutions of access selectionare either substantially simplified and restricted to individualcommunication flows, or arrive at excessive processing requirements whenconsidering a plurality of communication flows seeking globaloptimization. The invention identifies a need for both considering aplurality of communication flows when allocating the flows to one ormore access technologies, and a need for reduced processing requirementsand adaptations to existing application program interfaces, APIs, whenfacing the problems of implementing multi-access systems.

It is, consequently, an object of preferred embodiments of the inventionto provide a method and system for sequential access selection.

It is also an object of preferred embodiments of the invention toprovide a method and system for access selection adapted for coordinatedallocation of communication flows.

A further object of embodiments of the invention is to facilitate fastallocation of communication flows associated with particularrequirements for appropriate access selection.

Finally, it is an object of embodiments of the invention to enableadaptation to changing conditions and requirements in a multi-accesscommunications environment.

These objects are met by a method and system of access technologyselection, allocating a plurality of communication flows to one or moreof a plurality of access technologies included for communications in acommunications system by means of stored allocation preference values.

Preferred embodiments of the invention, by way of examples, aredescribed with reference to the accompanying drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates example preference values stored in memory, in thefigure represented by a table, according to the invention.

FIG. 2 demonstrates schematically access selection functionalityequipment according to the invention.

FIG. 3 illustrates updated example memory content, represented in thefigure by a preference value table, according to the invention.

FIG. 4 shows for an example embodiment of the invention extension ofmemory storage, as represented by tables in FIGS. 1 and 3, to providefor additional information qualifiers.

FIG. 5 demonstrates a flow chart schematically illustrating a fourthexample embodiment of the invention.

DETAILED DESCRIPTION

In the following description, for purpose of explanation, specificdetails are set forth such as particular architectures, interfaces,techniques, etc. in order to provide a thorough understanding of thepresent invention. However, it will be apparent to those skilled in theart that the present invention may be practiced in other embodimentsthat depart from these specific details.

In some instances, detailed descriptions of well-known devices,circuits, and methods are omitted so as not to obscure the descriptionof the present invention with unnecessary detail. All statements hereinreciting principles, aspects, and embodiments of the invention, as wellas specific examples thereof, are intended to encompass both structuraland functional equivalents thereof. Additionally, it is intended thatsuch equivalents include both currently known equivalents as well asequivalents developed in the future, i.e., any elements developed thatperform the same function, regardless of structure.

The invention discloses access selection in a communications system,wherein a user terminal or PAN has two or more communications flows andthere are two or more access technologies available.

Interdependencies tend to cause problem when selecting accessestechnologies for individual flows. A selection decision is likely toaffect other, future or past, access selections.

The following examples illustrate some sampled situations.

-   -   1. A candidate access technology is selected for a first        downlink flow (in direction towards user terminal or PAN). This        flow is subsequently mapped to a particular access configuration        of the selected access technology, e.g. a Radio Access Bearer,        RAB, of access technology WCDMA. The access configuration may be        specified, e.g. in technical system specifications or standards,        to also require resources for uplink direction. Such access        mapping, once the access technology is selected, is not always        under control of the multi-access selection functionality.        Selection of the particular access technology is thereby        inefficient given the conditions of the communication flows and        access technologies.    -   2. An access technology is selected for a first communications        flow. The flow is mapped to an access configuration, e.g. a best        effort bearer, which is not under control of the multi-access        selection functionality. Selection of the particular access        technology thereby introduces inefficiency, since the mapping        may not fulfill requirements of the communication flow.    -   3. An access technology is selected for a first flow and the        access technology is available for the user terminal. If        however, two different access technologies cannot be applied        simultaneously due to e.g. interference or terminal limitations;        there may be need for the flow to be reallocated if there is        more than one flow to allocate. The additional (re-)allocation        introduces allocation inefficiency.

The sample situations illustrate the need for ranking of accessselection preferences in relation to various access technologies orcommunication flows. According to the invention, interdependenciesbetween access selection decisions for individual communication flowsare expressed as constraints, or preferences, for access selectiondecisions that relate to groups, or bundles, of communication flows.

The access selection decisions of the various flows of a group or bundleof flows are often separated in time and cannot be consideredsimultaneously, in order not to introduce excessive communication delay.User communication flows start and stop more or less randomly from asystem perspective, and as they do so, access (re-)selection decisionsneed be made. To improve established access selection allocations, it isadvantageous to evaluate assignments from a “global” perspective,considering many, if not all, established access selection decisionsconcerning flow bundles of a particular user terminal or PAN, andpossibly also all user terminals/PANs. The considerable time requiredfor a perfect access selection allocation opts for improvements torender the access selection feasible for real time applications.

A first example embodiment of the invention provides for a method andsystem for access selection of communications flows, such that decisionscan be made efficiently for individual flows. This is a achieved byreflecting dependencies between access selection decisions throughpreference values of communication flows in relation to various bundlesof communication flows. Each preference value corresponds to a utilityvalue for a particular communication flow, indicating the preference ofthe allocation in relation to other allocations to the particular one ormore bundles, which the preference value refers to.

FIG. 1 illustrates example preference values stored in memory, e.g.random access memory, RAM, in the figure represented by a table,according to the first example embodiment. In the memory various accesstechnologies are included with a preference value. When considering anaccess technology A₁ for allocation of a communication flow, thepreference value is consulted. The preference value of access technologyA₁ is positive (+2) and indicates a positive utility of allocatingadditional one or more communication flows to the access technology. Inaccordance with the figure, also another access technology A₃ isincluded in memory and considered for allocating of the flow prior tomaking the selection decision. However, the preference value of accesstechnology A₃ is negative (−5) and indicates that further allocation ofcommunication flows to the access technology would have an adverseeffect on system performance. Also a third access technology A₅ isincluded in memory together with an associated preference value (+1). Inthe example of FIG. 1, communication flow f₁ is allocated to accesstechnology A₁. Allocation of communication flow f₁ to access technologyA₁ has an adverse effect on allocation of future communication flows toaccess technology A₃ due to interference, rendering the preference valueof access technology A₃ negative (−5).

Allocation of communication flow f₁ to access technology A₁ also affectsa third access technology A₅ and affects another communication flow f₃allocated to A₅. This impact is included in the memory, represented bythe table, as a related flow in a flow bundle. By inclusion of relatedflows in bundles, as illustrated in the example in FIG. 1, a pluralityof flows in a flow bundle can be considered.

The stored preference values, such as the one illustrated in the tableof FIG. 1, consequently comprises a number of entries. According to thefirst example embodiment as illustrated in FIG. 1, there is one entryfor each access technology that is available for assignment of futurecommunication flows. According to example embodiments described infurther detail below more than one entry for each access technology isnot excluded.

If an allocation selection decision is such that there is still apreference of using the allocated access technology also for futureallocations of communication flows, the preference value is positive.The greater the positive value, the greater is the preference.

If an allocation selection decision is such that it has a negativeimpact on future allocations to the particular access technology forfuture allocations of communication flows, the preference value isnegative. The greater the magnitude of the negative value, the greateris the adverse effect of selecting the access technology for futurecommunication flows.

A zero preference value indicates a neutral preference to allocatingfuture communication flows to the particular access technology.

According to the first example embodiment of the invention, thepreference values are used as input to access selection functionalityequipment, ASF, included in or connected to a user terminal or PAN. Inone example implementation it is included in a radio access network. Inanother example implementation it is included in a control unit of acommunications system. The ASF is schematically illustrated in FIG. 2.

Preference values <<p>> are input to access selection functionalityequipment <<ASF>>. A flow correlation module <<FCM>> for each userterminal or PAN preferably represents preference values of accessselection decisions in a lookup table temporarily stored in memoryconnected to a processing entity <<μ>> of the access selectionfunctionality equipment <<ASF>>. The values <<p>> are optionallycombined with other access selection criteria <<a>>. The accessselection functionality equipment <<ASF>> outputs a selection decision<<s>> for each of the flows <<f₁>>, <<f₂>>, <<f₃>> to be allocated to atleast one access technology <<A₁>>, <<A₃>>, <<A_(5>>.)

When an access selection decision is requested for a second flow f₂, thestored preference values, similar to those in the table of FIG. 1, areconsulted. When a candidate access technology, e.g. access technologyA₁, is evaluated by the ASF, the corresponding preference value in thelist is used. If the candidate access technology is actually allocatedto the flow f₂, the flow bundle is augmented to include the allocatedflow f₂. When a flow is terminated and ends, the flow is also removedfrom the flow bundle of the access technology. If the flow bundle set isempty, the entry for the access technology is preferably removed frommemory. The ASF equipment is preferably applied also for exampleembodiments of the invention described below.

FIG. 3 illustrates updated example memory content, represented in thefigure by a preference value table. The table representation illustratesan actual example allocation when a flow f₂ has started and flow f₃ hasended since the allocation was made as schematically represented inFIG. 1. In the table representation, flow f₂ has augmented the set ofrelated flows related to access technology A₁. Flow f₃ has been excludedfrom the set of flows related to access technology As. The preferencevalues have been adjusted accordingly.

In a second example embodiment, the entries in memory compriseadditional information indicators. Non-exclusive examples of suchinformation indicators are whether the various flows are directed fromor towards the user terminal or PAN, i.e. whether they are in uplink ordownlink direction, respectively, or whether the various communicationflows require a particular minimum bit rate or are best effortcommunication flows.

Also for the second example embodiment, the preference values in memoryare considered when allocating a communication flow to an accesstechnology. In the second example embodiment, however, the additionalinformation indicators are also consulted for a match to thecorresponding prerequisites of the flow to be allocated. The updating ofthe set of flows that are affected by an access technology beingallocated to a future allocation of one or more communication flows issimilar to the updating described for the first example embodiment andFIGS. 1 and 3. However, since there are one or more informationindicators, there is typically more than one entry for at least someaccess technology. There may still be situations, though, when there areonly single occurrences of included one or more access technologies.

In FIG. 4, the table representation of FIGS. 1 and 3 is extended by twocolumns representing information qualifiers <<Direction Indicator>>,<<Rate Requirement>>. The figure illustrate an example allocation, whereaccess technology A₁, was selected for downlink flow f₁, the accesstechnology providing a bi-directional bit rate of at least 64 kbit/s andthe flow f₁ being in downlink direction. Example entry number 1 of FIG.4 reflects that it is advantageous to allocate future flows in downlinkdirection requiring at most 64 kbit/s to access technology A₁. Also withreference to the example situation illustrated in FIG. 4, interferencebetween access technologies A₁ and A₃ are supposed to be known tointerfere. Consequently, in entry number 2, access technology A₃ isindicated as being related to the communication flow f₁.

For communication flows f₂ and f₃ access technology A₂ has been selectedfor best effort communication flows in downlink direction. Due to theremaining positive preference value, also future communication flows inuplink direction for best effort are likely to be allocated to accesstechnology A₂.

An application programming interface, API, is the interface that acomputer system, library or application provides in order to allowrequests for services to be made of it by other computer programs,and/or to allow data to be exchanged between them. Existing APIs forapplications to request communication flow setup are typically writtensuch that one flow is set up at a time. When a plurality ofcommunication flows are set up, this is made by sequentially setting upthe individual communication flows. When an application requires aplurality of communication flows, this imposes additional challengeswhen it comes to access technology selection, e.g. when the existingapplication including the API is used in a (new) ABC environment.

The invention identifies that implementation and performance gains areachieved by a particular method and system of ordering of thecommunication flows.

According to a third example embodiment of the invention, thecommunication flows of a multi-flow session are setup and orderedaccording to one or more predefined criteria for access technologyselection. When sequentially ordered according to the one or morepredefined criteria, the communication flows are preferably allocated tothe various access technologies, allocating the flows with greatestrequirements (e.g. greatest required bit rate) first. As a non-exclusiveexample, the communication flows are ordered according to bit raterequirements. Another non-exclusive example ordering criterion isdirection requirement (uplink/downlink). A further non-exclusivecriterion for ordering is candidate preference values, as will bedescribed in detail below in relation to a fourth and fifth exampleembodiment of the invention.

According to a fourth example embodiment of the invention, the accesstechnology allocation process is divided into two phases.

-   -   1. In the first phase, a preliminary allocation is executed        where each communication flow is preliminarily allocated to the        various access technologies as described for the example        embodiments above. For the preliminary candidate allocations,        the preference values are determined and updated as if the        communication flows were actually allocated to the various        access technologies. During the first phase such preliminary        candidate allocations are preferably executed for all        communication flows for which an allocation technology should be        selected. For each communication flow the greatest increase of        preference value is stored in memory as the access technologies        are investigated.    -   2. In the second phase, the preference value increases stored        during the first phase are ordered according to their size.

The flows providing the greatest preference value increases arepreferably allocated first, thereby improving efficiency of accesstechnology utilization.

FIG. 5 schematically illustrates a flow chart describing the fourthexample embodiment. In a first step <<S1>> counters and preference valueincreases are reset. For each communication flow <<CF>>, the accesstechnologies <<ATs>> are looped through <<S2>>. For each communicationflow <<CF #i>> and access technology <<AT #j>>, a preliminary allocationand preference value <<PV>> increase is determined <<S3>>. For eachcommunications flow <<CF #i>, the greatest preference value increase<<PV increase #i> is stored <<S5>>. The preliminary allocation isexecuted for all communication flows to be allocated <<S6>>. When allcommunications flows of interest have been preliminary allocated, thecommunication flows are arranged according to their greatest preferencevalue increase <<S7>>, as stored <<S5>>. The ordered list ofcommunication flows is then looped through <<S8>> and the variouscommunication flows are allocated to an access technology <<S9>>.

According to a fifth example embodiment of the invention, thepreliminary candidate allocation of flows as described in relation tothe fourth example embodiment is extended and executed for bundles offlows. After a first communication flow of the bundle has beenpreliminarily allocated as described for the fourth example embodimentabove, the process is repeated for the second communication flow of thebundle. Consequently, the required memory capacity for storage ofpreference values increases exponentially with the number of flows. In atypical and interesting situation, however, the number of flows ofinterest is two, limiting the memory requirement to the square of thememory capacity required for the fourth example embodiment. The requiredmemory capacity could generally be halved due to symmetries inallocation preference values. The greatest preference value increase isthen, unless redundant utilizing symmetries, stored for each pair offlows. The stored preference values are then ordered according to theirsizes for allocation of access technology as described for the fourthexample embodiment.

The example embodiments described above have been described in relationto a single user terminal or PAN. The advantages achieved from thepreference values are further explored in a method and systemconsidering a plurality of user terminals and PANs for globallyefficient access technology allocation, thereby substantially reducingthe complexity of access technology selection described in prior artcited above. The complexity reduction would render global or at leastlocal access selection, for a limited number of user terminals and PANs,feasible and would also allow regular access reselection with availableprocessing capacity of today.

A person skilled in the art readily understands that the receiver andtransmitter properties of, e.g., a user equipment are general in nature.The use of concepts such as access selection functionality equipment,ASF equipment, application program interfaces, APIs, or radio accesstechnology, PAT, within this patent application is not intended to limitthe invention only to devices associated with these acronyms. Itconcerns all devices operating correspondingly, or being obvious toadapt thereto by a person skilled in the art, in relation to theinvention.

The invention is not intended to be limited only to the embodimentsdescribed in detail above. Changes and modifications may be made withoutdeparting from the invention. It covers all modifications within thescope of the following claims.

1. A method of access selection in a multi-access communications systemfor allocating one or more communication flows to one or more of aplurality of access technologies, the method comprising, for one or moreof the communication flows: determining one or more preference values ofeach of the plurality of access technologies, the preference valuesreflecting whether it is advantageous to allocate additionalcommunication flows to the access technology; and storing the preferencevalues.
 2. The method of claim 1 wherein storing the one or morepreference values comprises storing a preference value linked to abundle of one or more communication flows affecting the preferencevalue.
 3. The method of claim 2 further comprising including acommunication flow allocated to an access technology in the bundlelinked to a preference value of the access technology.
 4. The method ofclaim 2 further comprising updating a preference value when acommunication flow is allocated to the access technology to which thepreference value refers.
 5. The method of claim 2 further comprisingupdating a preference value when a communication flow in the bundlelinked to the preference value is ended or terminated.
 6. The method ofclaim 1 further comprising associating the one or more preference valueswith one or more information qualifiers indicating at least one of acondition, a requirement, a lack of corresponding conditions or a lackof corresponding requirements, associated with the communication flowsfor allocation to the access technology.
 7. The method of claim 1further comprising associating the one or more preference values withone or more information qualifiers indicating at least one of aparticular condition and a particular requirement under which the one ormore preference values are relevant.
 8. The method of claim 1 furthercomprising executing a preliminary candidate allocation for allcommunication flows.
 9. The method of claim 8 further comprisingassociating a preliminary candidate allocation with a preliminarycandidate preference value update.
 10. The method of claim 8 furthercomprising determining, over the available access technologies, agreatest preference value increase of preliminary candidate update foreach communication flow or each pair of communication flows.
 11. Themethod of claim 10 further comprising: ordering the communication flowsaccording to their greatest preference value increase; and sequentiallyallocating the communication flows to the access technologies insequence of the ordering.
 12. The method of claim 1 further comprisingselecting the access technology based on the preference values ofcommunication flows associated with different user terminals or PersonalArea Networks (PANs).
 13. Access selection equipment for allocating oneor more communication flows to one or more of a plurality of accesstechnologies, the access selection equipment comprising: a processorconfigured to process one or more preference values determined for eachof the plurality of access technologies; and memory configured to storethe one or more determined preference values, wherein the preferencevalues reflect whether it is advantageous to allocate additionalcommunication flows to the access technology.
 14. The access selectionequipment of claim 13 further comprising an input configured to receiveat least one of an allocation policy or a preference value.
 15. Theaccess selection equipment of claim 13 further comprising an inputconfigured to receive additional access selection criteria.
 16. Theaccess selection equipment of claim 13 wherein the memory is furtherconfigured to store a preference value linked to a bundle of one or morecommunication flows affecting the preference value.
 17. The accessselection equipment of claim 16 wherein the memory is further configuredto include a communication flow allocated to an access technology in thebundle linked to a preference value of the access technology.
 18. Theaccess selection equipment of claim 16 wherein the processor is furtherconfigured to update a preference value when a communication flow isallocated to the access technology to which the preference value refers.19. The access selection equipment of claim 16 wherein the processor isfurther configured to update a preference value when a communicationflow in the bundle linked to the preference value is ended orterminated.
 20. The access selection equipment of claim 13 wherein theone or more preference values stored in memory are associated with oneor more information qualifiers indicating one or more of a condition, arequirement, a lack of corresponding conditions, or a lack ofcorresponding requirements, of communication flows for allocation to theaccess technology.
 21. The access selection equipment of claim 13wherein the one or more preference values stored in memory areassociated with one or more information qualifiers indicating one ormore of a condition, a requirement, a lack of corresponding conditions,or a lack of corresponding requirements, under which the one or morepreference values are relevant.
 22. The access selection equipment ofclaim 13 wherein the processor is configured to execute a preliminarycandidate allocation for all communication flows.
 23. The accessselection equipment of claim 22 wherein the processor is furtherconfigured to accompany the preliminary candidate allocation by apreliminary candidate preference value update.
 24. The access selectionequipment of claim 22 wherein the processor is further configured todetermine a greatest preference value increase of preliminary candidateupdate over the available access technologies for each communicationflow, or for each pair of communication flows.
 25. The access selectionequipment of claim 24 wherein the processor is further configured to:order the communication flows according to their greatest preferencevalue increase; and sequentially allocate the communication flows toaccess technologies in sequence of the ordering.
 26. The accessselection equipment of claim 13 wherein the processor is furtherconfigured to operate on the preference values of communication flows ofdifferent user terminals or Personal Area Networks (PANs).
 27. Acommunications system comprising: two or more user terminals or PersonalArea Networks (PANs); two or more access networks; and access selectionequipment configured to allocate communication flows of the two or moreuser terminals or PANs to at least one of the access networks, andcomprising a processor configured to operate on preference values of theone or more communication flows of the user terminals or PANs.